You don't mess with US immigration officials. That was the painful lesson learned by passengers on a P&O cruise ship recently as they travelled through the Land of the Free.

On a 10-week Alaska Adventure - a rare round-trip voyage from Southampton - the ship had already called at 10 American ports before it arrived in Los Angeles on May 26.

But the one-day visit turned into a nightmare when rigorous security checks took seven hours to complete. Every passenger was fingerprinted on both hands, retina scans were taken, and they were subjected to detailed passport examinations and questioned about their background.

The passengers, many of them elderly, have claimed that the extra checks were taken by spiteful immigration officials in retaliation to comments made about their over-zealous behaviour. They complained they were left to stand in queues in soaring temperatures, with no food or water, and with limited access to toilets.

The ship left Southampton on April 12, and had already visited the Caribbean, Central America and Alaska. It was on its way back to the Panama Canal when it stopped at Los Angeles. Because of the delays the the visit was extended by a day, and a call at Roatan in Honduras was cancelled.

A total of 15 stops were scheduled at US ports during the 72-night cruise, and passengers had all completed standard US immigration (ESTA) forms designed for multiple-entry trips.

The Daily Telegraph reports that 60-year-old John Randall, a retired dentist from Wigan, wrote to the Captain to complain about the treatment meted out by the US officials. ""We are holiday makers, here to try and enjoy ourselves - we are not potential inmates of Guantalamo Bay, and should not be treated as such."

A spokeswoman for P&O said today: "The delay in immigration procedures was largely to blame on issues with the Customs and Borer Protection computer systems, not aided by the verbal approach that a minority of our passengers, clearly frustrated by the delay, took with the local immigration officers.

"The US has a record for the most stringent and thorough security and entry requirements in the world, and they felt the need to enhance their security checks further, which they have the power to do. This is something that did not happen on our call in San Francisco, where formalities were completed in an acceptable timeframe.

"Whilst the entire process took seven hours, passengers were called in deck order and we estimate the maximum queue length to have been one hour."

Miami attorney James Walker, who specialises in pursuing legal actions on behalf of cruise passengers, displayed a rare note of American humour when he observed: "A UK luxury cruise turns into a US Customs and Border Patrol 'revenge interrogation' of geriatric Brits? The US war on terror continues. They are lucky Homeland Security didn't waterboard them ...."